In the related art, a drive device for an opening/closing body, is known, which is provided with an opening/closing body which opens and closes an opening in a vehicle body, an opening/closing-body drive motor which drives the opening/closing body in an opening and closing manner by rotating forwardly and reversibly, a battery which generates a driving current for the opening/closing-body drive motor, a supplier which supplies driving current that is generated by the battery to the opening/closing-body drive motor, and a switching device which switches forward/reverse rotation direction of the opening/closing-body drive motor. At least one of the supplier and the switching device is provided with a relay switch (Patent Literature 1).